<!DOCTYPE html>
<html>

<head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <link rel="stylesheet" href="../bootstrap-5.1.3-dist/css/bootstrap.css">
    <script src="../bootstrap-5.1.3-dist/js/bootstrap.js"></script>
</head>

<body class="container">
    <h3 class="mb-4">设置一个列宽</h3>
    <div class="row">
        <div class="col border py-3 bg-light">左</div>
        <div class="col-7 border py-3 bg-light">中</div>
        <div class="col border py-3 bg-light">右</div>
    </div>
    <div class="row">
        <div class="col-3 border py-3 bg-light">左</div>
        <div class="col border py-3 bg-light">中</div>
        <div class="col border py-3 bg-light">右</div>
    </div>
</body>

</html>